1. Field of the Invention
The present invention relates to a transparent polymer, particularly to a polymerizable composition suitable as a raw materlal for producing an ophthalmic lens. More specifically, it relates to a polymerizable composition suitable for producing a transparent polymer which is free from coloring in the heat treatment carried out for improving the adhesion of a coating agent prior to the application of the coating agent to the transparent polymer and which has sufficient properties as an ophthalmic lens such as a high refractive index, a low specific gravity, dispersibility, light resistance, hardness, dyeability, impact resistance and odorless properties in resin processing. Further, the present invention relates to a polymer formed from the above polymerigable composition, particularly to an organic glass and an ophthalmic lens.
2. Description of the Related Art
Studies have been hitherto made of organic glass, which is expected to substitute inorganic glass. However no satisfactory organic glass has been obtained so far. For example, a polymer obtained by the polymerization of a monomer composed mainly of methyl methacrylate or diethyiene glycol bis(allylcarbonate) is being used as an optical material or lens. However, the refractive index of this polymer is as low as about 1.50.
In recent years, attempts to increase the refractive index, have been made by introducing sulfur into the molecular structure of a polymer. For example, Japanese Laid-open Patent Publication No. 164501/1984 discloses a polymer produced from a distyrene compound containing a sulfide structure. Japanese Laid-open Patent Publications Nos. 300201/1989 and 309002/1989 disclose a polymer produced by the addition polymerization of a vinyl compound and a polythiol compound. The defect with these polymers is that their light resistance is poor.
Further, Japanese Patent Publication No. 51161/1990 discloses organic glass formed of a copolymer produced from the monomer of the following formula, ##STR2## and other monomers polymerizable with the above monomer. The problem with the above organic glass is that when it is heat-treated for improving the adhesion of a coating agent prior to the application of the coating agent, it turns yellowish as a whole.
Further, Japanese Laid-open Patent Publication No. 198510/1983 discloses organic glass formed by the polymerization of a monomer composition comprised of a dimer of .alpha.-methyl styrene, i.e., 2,4-diphenyl-4-methyl-1-pentene, methyl methacrylate and ethylene glycol dimethacrylate. Although it is transparent, this organic glass cannot be used as an ophthalmic lens, since it has a low refractive index and is insufficient in properties such as dyeability.